1. Field of the Invention
The present invention relates generally to a two-wheeled vehicle. More particularly, the invention relates to a two-wheeled vehicle in which the inclusive structure of the vehicle body has the center of gravity thereof deviated from the vehicle center line in either transverse direction.
2. Description of Relevant Art
Two-wheeled vehicles generally comprise a steering system inclusive structure including a handlebar, a front fork and the like and provided with a front wheel, and a vehicular body inclusive structure comprising a vehicle frame, a driver's seat and the like and provided with a rear wheel. The steering system inclusive structure is transversely turnable and is pivotably connected with the vehicular body inclusive structure so as to be capable of steering operation. The connection of the steering system inclusive structure relative to the vehicular body inclusive structure is arranged such that the front fork is vertically inserted through a head pipe secured to the front end of the vehicle frame, while in order to secure straight driving operation of the vehicle the head pipe and the front fork have the axes thereof inclined with respect to the vertical direction, i.e., the front fork which bears a shaft of the front wheel at the lower end thereof has a caster angle.
Among the foregoing two-wheeled vehicles, there are those in which the vehicular body inclusive structure has the position of the center of gravity thereof deviated in either transverse direction from the vehicle center line extending longitudinally through the head pipe. Such deviation of the center of gravity is provided, for example, in two-wheeled vehicles of a motorized type which are driven by the power of an engine, in which a power unit including the engine as a constituent part thereof is arranged on either lateral side of the rear wheel.
However, if the position of the center of gravity of the vehicular body inclusive structure is deviated from the vehicle center line, the vehicular body inclusive structure tends to fall toward the gravity deviated side. For this reason, it has been proposed to check such falling by what is referred to as the "cut-in motion" of the steering system inclusive structure.
Due to the cut-in motion of the steering system inclusive structure, a twisting force caused by the caster angle acts on the vehicular body inclusive structure, thus exerting a raise-up action on the vehicular body inclusive structure such that the position of the center of gravity is corrected in the transverse direction. In this manner, the two-wheeled vehicle can be driven while the dynamic balance thereof is maintained.
As a result, corresponding to the correction of the position of the center of gravity, the entire two-wheeled vehicle inclines with respect to the vertical direction, to a slight extent, and with such inclined position travels in a straight course.
The present invention effectively overcomes the problems encountered with respect to the foregoing considerations in a vehicular body inclusive structure which has the center of gravity thereof deviated from the vehicle center line.